/*
 * Copyright � 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace Spring.Objects.Factory.Config;

/// <summary>
/// Implementation of <see cref="IVariableSource"/> that
/// resolves variable name against command line arguments.
/// </summary>
/// <author>Aleksandar Seovic</author>
[Serializable]
public class CommandLineArgsVariableSource : IVariableSource
{
    private const string DEFAULT_ARG_PREFIX = "/";
    private const string DEFAULT_VALUE_SEPARATOR = ":";

    private string argumentPrefix = DEFAULT_ARG_PREFIX;
    private string valueSeparator = DEFAULT_VALUE_SEPARATOR;

    private string[] commandLineArgs;
    protected IDictionary<string, string> arguments;

    private object objectMonitor = new object();

    /// <summary>
    /// Default constructor.
    /// Initializes command line arguments from the environment.
    /// </summary>
    public CommandLineArgsVariableSource()
    {
        this.commandLineArgs = Environment.GetCommandLineArgs();
    }

    /// <summary>
    /// Constructor that allows arguments to be passed externally.
    /// Useful for testing.
    /// </summary>
    public CommandLineArgsVariableSource(string[] commandLineArgs)
    {
        this.commandLineArgs = commandLineArgs;
    }

    /// <summary>
    /// Gets or sets a prefix that should be used to
    /// identify arguments to extract values from.
    /// </summary>
    /// <value>
    /// A prefix that should be used to identify arguments
    /// to extract values from. Defaults to slash ("/").
    /// </value>
    public string ArgumentPrefix
    {
        get { return argumentPrefix; }
        set { argumentPrefix = value; }
    }

    /// <summary>
    /// Gets or sets a character that should be used to
    /// separate argument name from its value.
    /// </summary>
    /// <value>
    /// A character that should be used to separate argument
    /// name from its value. Defaults to colon (":").
    /// </value>
    public string ValueSeparator
    {
        get { return valueSeparator; }
        set { valueSeparator = value; }
    }

    /// <summary>
    /// Before requesting a variable resolution, a client should
    /// ask, whether the source can resolve a particular variable name.
    /// </summary>
    /// <param name="name">the name of the variable to resolve</param>
    /// <returns><c>true</c> if the variable can be resolved, <c>false</c> otherwise</returns>
    public bool CanResolveVariable(string name)
    {
        lock (objectMonitor)
        {
            if (arguments == null)
            {
                InitArguments();
            }

            return arguments.ContainsKey(name);
        }
    }

    /// <summary>
    /// Resolves variable value for the specified variable name.
    /// </summary>
    /// <param name="name">
    /// The name of the variable to resolve.
    /// </param>
    /// <returns>
    /// The variable value if able to resolve, <c>null</c> otherwise.
    /// </returns>
    public string ResolveVariable(string name)
    {
        lock (objectMonitor)
        {
            if (arguments == null)
            {
                InitArguments();
            }

            string retValue;
            arguments.TryGetValue(name, out retValue);
            return retValue;
        }
    }

    /// <summary>
    /// Initializes command line arguments dictionary.
    /// </summary>
    protected virtual void InitArguments()
    {
        this.arguments = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);

        foreach (string arg in commandLineArgs)
        {
            int separatorIndex = arg.IndexOf(valueSeparator);
            if (arg.StartsWith(argumentPrefix) && separatorIndex > argumentPrefix.Length)
            {
                string argName = arg.Substring(argumentPrefix.Length, separatorIndex - argumentPrefix.Length);
                string argValue = arg.Substring(separatorIndex + valueSeparator.Length);
                this.arguments[argName] = argValue;
            }
        }
    }
}
